Well, the display only behaved for a week before staying on constantly again. Removed the radio again, but this time i also disconnected the connectors buried behind the radio. Used a multimeter and found that the wire which goes from the aerial amplifier feed on the radio has 12v as expected with radio on. This wire feeds the aerial amplifier in the estate, but also sends a radio on signal to pin 8 of the mid. The problem is when radio is of, the wire still had 4,6 volts. Which obviously is enough for the mid to think the radio is on and then stay lit all the time. Anyway even with the radio removed, this wire has constantly around 4,6v. Which looks to me as a wiring problem somewhere between the dash and the tailgate. Disconnected the wire from behind the radio to mid, and mid works fine, but obviously without radio info.
So my question is if anybody knows which route the aerial powerfeed follows from behind the radio to the tailgate on a pfl estate? I've checked the obvious problem area where the wires enter the tailgate, and though the wires there are in a bad shape, reinsulating Them didnt help.